Mechanisms of invasion resistance: competition among intertidal mussels promotes establishment of invasive species and displacement of native species

Abstract

Understanding interactions between invasive species and recipient communities is essential to determining whether invasive species will become established and spread. In this study, we explored the role of competition and the specific mechanisms of interaction in limiting the spread of the Mediterranean bay mussel Mytilus galloprovincialis within a Pacific Northwest invasion front. We examined the role of direct (interference) and indirect (exploitation) mechanisms of competition among M. galloprovincialis and 2 native mussels (M. trossulus and M. californianus). As the fastestgrowing organisms are often competitively dominant in space-limited systems, such as rocky intertidal communities, we used changes in relative performance (growth and survival) in monocultures and polycultures to assess interactions among mussels. Performance of M. galloprovincialis was always greater than that of the 2 native species of mussels in both field and laboratory manipulations of species composition and density, indicating that interspecific competition did not strongly limit the growth or survival of the invader. Moreover, the presence of M. galloprovincialis consistently led to both reduced growth and survival of M. trossulus. Laboratory studies of mussel feeding and behavior revealed M. galloprovincialis to be a robust interference competitor. The invader restricted movement, smothered and interfered with filter feeding of the 2 native species of mussels. Rather than limiting invasion, interference competition gave M. galloprovincialis a competitive advantage over the native mussels. Our results suggest M. galloprovincialis may have contributed to the displacement of M. trossulus along much of its historic southern range.

Behavior and survival ofMytiluscongeners following episodes of elevated body temperature in air and seawater

“…smaller effect sizes) and enjoyed higher survival following elevated body temperature than did M. trossulus, in accord with our expectations based on a number of other studies (Braby and Somero, 2006b;Lockwood et al, 2010;Lockwood and Somero, 2011;Schneider, 2008;Schneider and Helmuth, 2007;Tomanek and Zuzow, 2010). These data add to the growing literature demonstrating that, among mussel species, disparate combinations of physiology and behavior play a crucial role in ecological success of species, notably in the context of biological invasions (de Zwaan et al, 1991;Lockwood and Somero, 2011;Nicastro et al, 2010;Schneider et al, 2005;Shinen and Morgan, 2009). Our data also provide evidence that changes in behavior may be sensitive indicators of underlying physiological perturbations elicited by environmental stress.…”

Invasion resistance on rocky shores: direct and indirect effects of three native predators on an exotic and a native prey species

“…Additionally, further invasion success will likely have wide-ranging effects on intertidal community structure. Since M. galloprovincialis is competitively robust among native mussels (Shinen & Morgan 2009), the mussel bed community structure will change if native mussels decline. In particular, displacement of M. californianus by the smoother-shelled M. galloprovincialis may lead to declines in native epibiont species diversity and richness (J.…”

“…Strong prey preferences of Nucella ostrina may also influence competitive hierarchies among native and invasive mussels (Carroll & Highsmith 1996, Navarrete & Menge 1996 and may affect the decline of Mytilus trossulus and the invasion by M. galloprovincialis. M. galloprovincialis is competitively dominant over M. trossulus and is the fastest growing of the 3 species of mussels within the invasion front (Shinen & Morgan 2009). Because whelks prefer M. trossulus to M. galloprovincialis, predation by N. ostrina might have exacerbated the negative competitive effects of M. galloprovincialis on native mussels and contributed to the decline of the native species.…”

“…This species is in decline and is uncommon along the open coast in our study region. It is competitively inferior to M. californianus and M. galloprovincialis and suffers high mortality in culture with heterospecifics (Shinen & Morgan 2009). In May 2005, mussels were haphazardly assigned to 7 replicates of 3 experimental treatment types: M. californianus monoculture (n = 40), M. galloprovincialis monoculture (n = 40), and polyculture (n = 40; 20 M. californianus and 20 M. galloprovincialis).…”

“…Physiological limitations and competitive interactions among native and invasive mussels are not likely to restrict further invasion of M. galloprovincialis. Transplants of the invader experience high growth and survival rates in the absence of predators and are competitively robust among 2 native species of mussels on the open coast (Shinen & Morgan 2009). Moreover, M. galloprovincialis reduces growth and survival of M. trossulus (Shinen & Morgan 2009) and may be contributing to the decline of M. trossulus in the southern extent of its range (Geller 1999).…”